Forms a trilogy along with One (2002) and Trilogy: Two (2002), the main characters of this one being the supporting actors in the other ones, and vice versa. The three movies have some scenes in common which are shown from a different point of view according to the storyline we're following.
In the credits, Catherine Frot is credited for playing Jeanne Costes, and Ornella Muti for playing Cécile Rivet. During the movie, Frot's character is caller Jeanne Rivet, and Muti's character is called Cécile Costes.